Process for dimerizing diarylamines

ABSTRACT

Dimers of diarylamines are prepared by a process comprising treating a diarylamine-perchlorate salt with an oxidizing agent in an acidic medium. Exemplary of the products obtained is 4,4&#39;&#39;dianilino-1,1&#39;&#39;-binaphthyl, which is made by treating N-phenylAlpha -naphthylamine-perchlorate with chromium trioxide in acetic acid and water. The products thus produced are useful antioxidants in lubricants.

United States Patent 1 Braid (4 Sept. 18, 1973 PROCESS FOR DIMERIZINGDIARYLAMINES [75] lnventor: Milton Braid, Westmont, NJ.

[73] Assignee: Mobil Oil Corporation, New York,

[22] Filed: Jan. 13, 1971 [21] App]. No.: 106,248

[52] US. Cl. 260/576, 260/571 [51] int. Cl. C07c 87/64 [58] Field ofSearch 260/576, 571

[56] References Cited UNITED STATES PATENTS 4/1970 Braid et al. 260/576OTHER PUBLICATIONS Peeler, A. C. S. Division of Petroleum Chemistry,Pre-.

prints 10(2), D-ll9 (1965).

Theilheimer, Synthetic Methods of Organic Chemistry, lnterscience Pub.,Inc.: NY. Vol. 2 (1949), No. 633. Vol. l0 (1956), No. 565.

Primary Examiner-Lewis Gotts Assistant Examiner-C. F. WarrenAttorney0swald G. Hayes, Andrew L. Gaboriault, Raymond W. Barclay andClaude E. Setliff [57] ABSTRACT perchlorate with chromium trioxide inacetic acid and water. The products thus produced are usefulantioxidants in lubricants.

9 Claims, No Drawings PROCESS FOR DIMERIZING DIARYLAMINES BACKGROUND OFTHE INVENTION 1. Field of the Invention The invention relates to aprocess formaking carboncarbon linked dimers of N-phenyl-a-naphthylamine(PAN), N-phenyl-B-naphthylamine (PBN) and substituted derivativesthereof. More particularly, the inven tion relates to making such dimersby reacting an amine-perchlorate salt with an oxidizing agent, as forexample a metal oxide, in an acidic solvent medium.

2. Summary of the Prior Art The oxidation of PAN with chromium trioxidein a mixture of acetic and sulfuric acids has been reported by R. L.Peeler, A.C.S. Division of Petroleum Chemistry, Preprints l (2), D-1l9(1965). However, as will appear hereinafter, it has been found thatyields of the dimer, considered by Peeler to be crude N,N'-diphenylnaphthidine, are low when PAN, chromium trioxide and a mixtureof acetic and sulfuric acids are reacted together.

US. application Ser. No. 537,639, filed Mar. 28, 1966, in the names ofMilton Braid and Derek A. Law, now US. Pat. No. 3,509,214, discloses aprocess for producing a mixture of dimers, trimers and tetramers byoxidizing N-arylnaphthylamines with air and various other oxidizingagents such as potassium permanganate, lead dioxide, manganese dioxideand hydrogen peroxide. Although mass spectral data indicated that about42% of dimer was obtained in the oxidation of N-phenyl-a-naphthylaminewith potassium permanganate, separation of dimers of specific structurewas impractical.

SUMMARY OFTHE INVENTION DESCRIPTION OF SPECIFIC EMBODIMENTS As has beenmentioned, the oxidation of N-phenyl-a naphthylamine (hereinafterreferred to as PAN) with chromium trioxide in, a mixture of acetic andsulfuric acids has been reportedto produce the dimer (4,4-dianilino-1,1'-dinaphthy1). It was found, however, that the yield ofcarbon-carbon dimer which could be isolated from this system amounted toonly a'very small amount, based on the amine. It has been surprisinglydiscovered that if the perchlorate salt of a diarylamine is used insteadof the amine per se, good yields are obtained upon reacting such salt ina special oxidizing medium.

In general aspect, the inventive process involves the presence in thesystem of an amine perchlorate salt which does not de-protonate duringthe oxidation. Perchloric acid reacts smoothly with diarylamines to formsalts which appear to be stable during oxidation.

The best yields ofdimer. have been obtained with the amine perchloratesaltsby oxidizing same with a metal oxide, such as chromium oxide, inthe presence of acetic acid and water. In carrying out this reaction,the salt may be preformed by the addition of peracid to amine, or theproduct may be obtained by the metal oxide oxidation of the salt formedin situ in an organic acid me-v dium. Such acid medium may includeaqueous acetic, propionic or trifluoroacetic acid. Of these, acetic acidis preferred. This latter method is preferably carried out just at thesolubility limit of amine in the system, i.e., the system is saturatedwith the amine. The in situ reactions may be carried out in the presenceof an inert solvent, such as water or one of the organic solventsmentioned below for use in making the preformed salt.

When the salt is preformed, its preparation may be carried out in thepresence of an inert organic solvent, such as benzene. Other solventswhich may be used include cyclohexane, hexane and isooctane. In general,any inert organic solvent may be used, but those in which the salt isinsoluble are preferred because the salt is easily removed byfiltration.

Oxidation of the amine perchlorate salt is accomplished at a temperaturewithin the range of from about 0C. to about 25C., preferably from about0C. to about 10C.

In addition to chromium trioxide, which is the preferred metal oxide,other oxidizing agents may be used. They include lead dioxide, nitrousacid, nitric acid, potassium permanganate, manganese dioxide andhydrogen peroxide.

Having described .the process in general terms, the following willspecifically illustrate the invention. It will be understood that thematter following is intended for illustrative purposes only.

EXAMPLE I To a solution of g. of PAN in 600 ml. of glacial acetic acidwas added while stirring during 0.5 hour a solution of 25 g. of chromiumtrioxide in ml. of acetic acid, 50 ml. of water and 36 ml. of cone.sulfuric acid. Stirring was continued for 0.5 hour, and the reactionmixture was poured into about 2 l. of water. The solids whichprecipitated were collected and extracted with ethanol. The residueafter evaporation of the ethanol, 20.8 g., was extracted with petroleumether and the residue was crystallized from ethyl acetate. There wasfinally obtained a total of 1.5 g. of 4,4'-dianilino- 1,1 -binaphthyl.The fraction melting at ISO-182C (grey solids), gave the followinganalysis:

Calcd for C l-1 M: C, 88.04%; H, 5.54%; N, 6.42%; M01. Wt. 437

Found: C, 87.61%; H, 5.91%; N, 6.27%; M01. Wt.

Example 1 illustrates the use of prior art reactions such as the onedisclosed by Peeler as mentioned above.

Example 2 To 43.8 g. of PAN dissolved in 400 ml. of glacial acetic acidthere were added 56 ml. of water and 30.8 g. of 71.4% perchloric acid.To the resulting mixture there was added during 0.25 hour while stirringa solution of 7 g. of chromium trioxide in 20 ml. of water. After anadditional 10 minutes of stirring, 450 ml. of water was added and thesolids in the reaction mixture were collected by filtration, giving 48.1g. The solids were extracted with benzene to yield 43 g. (98%) of thecrude 4,4-dianilino-1,l-binaphthyl. The pure dimer was isolated bycrystallization from benzene, from ether, or from ethyl acetate afterremoval of the benzene by evaporation or distillation. The dimerobtained by crystallization from benzene, nearly white crystals, meltedat 182-l83C and gave the following analysis:

Calcd for C H N C, 88.04%; H, 5.54%; N, 6.42%; M01. Wt. 437

Found: 7 C, 88.81%; H, 5.85%; N, 6.81%; M01 Wt. 422

EXAMPLE 3 To a solution of 99.3 g. of N-(l,1,3,3-

tetramethylbutyl-phenyl)-l-naphthylamine in 500 ml. of glacial aceticacid cooled to 25C there was added while cooling 49 g. of 71.4%perchloric acid. When the resulting solution had cooled to 15C therewere added a further 75 ml. of acetic acid and 75 ml. of water. To theresulting reaction mixture there was added during 1 hour at 10C asolution of 10.5 g. of chromium trioxide in 30 ml. of water. Thereaction mixture was stirred at 1020C for one additional hour, 200 ml.of water was added, and the solids were collected by filtration (108.3g.). The dimer, N,N-di-( 1,1,3,3-tetramethylbutylphenyl)-l,l-naphthidine, was obtained by crystallizationfrom benzene as white crystals, melting at 159-161C.

Anal. Calcd for C ll- N N, 4.24%; M01. Wt. 661

Found: C, 86.36%; H, 8.46%; N, 4.24%; M01. Wt. 633

EXAMPLE 4 To 4.38 g. of PBN dissoled in 80 m1. of glacial acetic acidthere was added 3.08 g. of 71.4% perchloric acid. To the resultingreaction mixture there was added during 5 minutes a solution of 0.7 g.of chromium trioxide in 2 ml. of water. The reaction mixture was stirredfor an additional minutes and was then poured into 400 ml. of water.There was collected from the aqueous mixture 2.44 g. of crude product byfiltration, from which the dimer, 1,] '-bis(N-phenyl-Z-naphthylamine), awhite solid melting at l67-168C., was obtained.

The dimers produced in the process of this invention impart antioxidantproperties to lubricants. These include mineral oils, both paraffinicand naphthenic, as

well as synthetic lubricating oils such as polymerized olefins,polymerized alkylene oxides and the like, and esters. Representative ofsynthetic esters are diesters from monohydric alcohols and dicarboxylicacids, and such esters as those made from polyhydric alcohols andmonocarboxylic acids. Preferred among the esters prepared usingpolyhydric alcohols are those from pentaerythritol and a monocarboxylicacid containing from about five to about 9 carbon atoms (or mixtures ofsuch acids).

The following will specifically illustrate the use of the dimersproduced in Examples 2 and 3.

The product was tested in a catalytic oxidation test for lubricants,using as the base medium a synthetic ester lubricant prepared byesterifying a mixture of commercial grades of valeric and pelargonicacids with a technical grade of pentaerythritol (containing about 12% ofdipentaerythritol). The test composition was subjected to a stream ofair bubbled therethrough at a rate of 5 liters per hour. This wascontinued for 24 hours at 450F. Lead was present in the composition.

Inhibition caused by the additives was rated on the basis of preventionof oil deterioration by measuring the increase in acid formation orneutralization number (NN) and kinematic viscosity occasioned byoxidation. The following table shows the results.

Conc. NN Increases as Additive Wt.% Increase KV at F. None 8.25 5 8 54,4'-dianilino l l '-binaphthyl 1 3.05 17 4,4'-di-(p-l ,1 ,1 3,3-tetramethylbutylanilino l ,1 '-binapht.hyl 0.75 3.38 3 8 Havingdescribed the invention, what is claimed is:

l. A process for oxidatively dimerizing an amine selected from the groupconsisting of N-phenyl-anaphthylamine, N-phenyl-B-naphthylamine and thesubstituted members thereof, wherein the sbustituents are selected fromthe group consisting of C ,-C alkyl, C -C alkoxy and nitro consistingessentially of the step of allowing a perchlorate salt of said amine todimerize at a temperature within the range of from about 0C to about 25Cin the presence of a mixture consisting essentially of 1) an oxidizingagent selected from the group consisting of chromium trioxide, leaddioxide, nitrous acid, nitric acid, potassium permanganate, manganesedioxide and hydrogen peroxide and (2) an organic acid selected from thegroup consisting of acetic acid, propionic acid and trifluoroaceticacid.

2. The process of claim 1 wherein the perchlorate salt is prepared priorto treatment with said mixture.

3. The process of claim 1 wherein the perchlorate salt is formed insitu.

' 4. The process of claim 1 wherein the organic acid is saturated withN-phenyl-a-naphthylamine.

5. The process of claim 1 wherein the organic acid is saturated withN-phenyl-B-naphthylamine.

6. The process of claim 1 wherein the organic acid is saturated with N-ll ,3 ,3-tetramethylbutylphenyl )-anaphthylamine.

7. The process of claim 1 wherein the oxidizing agent is chromiumtrioxide.

8. The process of claim 1 wherein the acid is acetic acid.

9. The process of claim 1 wherein water is present in said mixture.

3 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.375999 Dated September 18, 1 W) 'inventor(s) Milton Braid It is"certified that error appears in the above-identified patent and thatsaid Letters Patent are hereby corrected as shown below:

g- 1 Column 3, line 35, dissoled should be dissolved Column A, line 21,-1,1,13,3" should be :3:3 I ColumnA line 49, "DI-1,1633" sheuld be.

i N (1 u -9323 *f Signed and sealed this 25th day of December 1973.

(SEAL) Attest:

EDWARD M.FLET CHEB,JR. RENE D. TEGTMEYER Y Attesting Officer ActingCommissioner of Patents

2. The process of claim 1 wherein the perchlorate salt is prepared priorto treatment with said mixture.
 3. The process of claim 1 wherein theperchlorate salt is formed in situ.
 4. The process of claim 1 whereinthe organic acid is saturated with N-phenyl- Alpha -naphthylamine. 5.The process of claim 1 wherein the organic acid is saturated withN-phenyl- Beta -naphthylamine.
 6. The process of claim 1 wherein theorganic acid is saturated with N-1,1,3,3-tetramethylbutylphenyl)- Alpha-naphthylamine.
 7. The process of claim 1 wherein the oxidizing agent ischromium trioxide.
 8. The process of claim 1 wherein the acid is aceticacid.
 9. The process of claim 1 wherein water is present in saidmixture.